In the 1970s, psychologist James Laird began an experiment where he asked volunteers to adopt different facial expressions.

Some of the participants were told to look angry by furrowing their eyebrows and clenching their teeth. Others were asked to smile and look happy.

Laird then tested their mood and found that people who were smiling - even though their smile was fake - felt significantly happier than those who had been frowning.

They also found things funnier. So try it today. Smile as widely as you can for up to a minute, even if you don't feel like it.

Some psychologists even recommend sticking a pencil in your mouth and gripping it with your teeth to help your muscles lift into a mega-watt grin (if you put the pencil between your lips, it makes you frown).

You might feel like an idiot but it will soon lift your mood for real.